Tape capacitor



Jan. 30, 1962 B. L. DAVIS ETAL 3,019,150

TAPE CAPACITOR Original Filed March 15, 1955 INVENTORS BENJAMIN L. DAV/SW/LBUR G NYBERG ATTORNEY United States Patent Ofifice 3,019,150 PatentedJan. 30, 1962 13 Claims. (Cl. 156--184) (Granted under Title 35, US.Code (1952), sec. 266) The invention described herein may bemanufactured and used by or for the Government of the United States ofAmerica for governmental purposes without the payment of any royaltiesthereon or therefor.

This application is a division of our copending application Serial No.494,592, filed March 15, 1955, now abandoned.

The present invention relates to a tape capacitor and more particularlyto a tape capacitor which is made from a modular wafer, and tape ofcertain physical characteristics.

An object of the present invention is to provide a capacitor for use inconjunction with a modular system of electronic components.

Another object is to provide a capacitor which is relatively easy tomanufacture, and is made of readily available material.

A further object is to provide a capacitor which has a high capacitance,in a minim-um volume.

Still another object is to provide a capacitor construction which mayconveniently be made in a variety of shapes and sizes.

Other objects and many of the attendant advantages of this inventionwill be readily appreciated as the same becomes better understood byreference to the following detailed description when considered inconnection with the accompanying drawings wherein:

FIG. 1 is a side view of a wafer having one plate of a capacitorthereon;

FIG. 2 is a plan view of the device of FIG. 1;

FIG. 3 is a perspective view of the device of FIG. 1;

FIG. 4 is a side View of a strip of tape forming a component of thecapacitor of the invention;

FIG. 5 is a side view of the tape of FIG. 4 after it has been treated;

FIG. 6 is a side view of the tape of FIG. 5 with a coatirrg shown insection, applied to one surface thereof;

FIG. 7 is a perspective view, partly broken away, of a capacitor madeaccording to the invention;

FIG. 8 is a side view of a laminated tape used in a modification of theinvention, with the coating shown in section.

FIG. 9 is a side view of a laminated tape used in a second modificationemploying an insulating layer and coating, both being shown in section.

FIG. 10 is a perspective view of a modification of the invention usingthe tape shown in FIG. 8, and

FIG. 11 is a perspective view of a modification using the tape shown inFIG. 9.

Referring now to the drawings, wherein like reference charactersdesignate like or corresponding parts throughout the several views,there is shown in FIGS. 1, 2 and 3 a generally square, notched wafer 10having on one surface 'a silvered pattern 12 covering the large centralpart thereof and a smaller silvered pattern 14 near a notch 16. Thesilvered pattern 12 is generally square, although this shape is notcritical, and has a leader 18 connecting it to the notch 22. The waferis made of an insulating material, preferably a ceramic, but may also bemade of glass, or of plastic laminations. The patterns 12 and 14preferably contain silver particles and a resin binder to constitutethem as conductors, although other conductive materials maybe usedinstead of silver. Pattern 12 forms one plate of the capacitor, andpattern 14 a lead for the other plate.

The patterns 12 and 14 may be placed on the wafer 10 by screening, photooffset printing, painting through a stencil, or any other rapid means.After deposit the patterns are wet and week until wafer 10 has beenfired at an elevated temperature ('01500 F. for ceramic wafers or800-850 F. for glass wafers or an appropriately lower temperature forplastic laminations) to permanently metalize the patterns.

In FIG. 4 there may be seen a piece of tape 24, which may be made ofasbestos paper, glass fibers, paper, or plastic. It is preferablyporous, for a reason to be hereinafter set forth. The tape 24 is madeinto a conductor by any convenient means. Preferably it is sprayed onboth sides with a formulation comprising silver powder in a binder andsolvent. The silver is represented by the dots in FIG. 5. The bindercomponent may be a silicone resin or an epoxy resin, for instance. Thesolvent component may be toluene, benzene or butyl cellosolve, forinstance.

After the tape 24 has been sprayed, and is heavily impregnated withsilver, it is sprayed again, on one side only, with a dielectricmaterial 26, thus giving the form of tape shown in FIG. 6. Dielectric 26is comprised of a resin binder similar to the binder noted above, andfinely ground ceramic dielectric materials. The dielectric materials arepreferably of the titanate family such as barium titanate and strontiumtitanate, and may comprise a mixture of two or more of such titanates.The materials are of a particle size of the order of 5 microns orsmaller. Dielectric 26 also contains a solvent similar to the abovenoted solvent. In some instances, where a very low capacitance willsuflice, the titanate may be omitted and a thicker coat of resinemployed.

The tape, as shown in FIG. 6, is cut into pieces the size of the pattern12 on wafer 10, in the embodiment shown, the tape is cut into a square.vThe square of tape is placed on the pattern, care being taken to insurethat no air is trapped under the tape. At this time, the resin of thepattern 12 has been fired off in the case of ceramic or glass wafers orhas hardened in the case of plastic wafers but the resin employed as abinder in dielectric 26 being in its uncured state is tacky, so that agluing action is obtained. Conveniently, any air which may be entrappedby the square of tape is forced out through the pores thereof by theapplication of pressure (less than 50 p.s.i.). It will be apparent thatpattern 12 forms one plate of the capacitor; material 26, the dielectricand tape 24, the other plate of the capacitor. A leader 28 of the tapeof FIG. 5 connects the tape 24 with pattern 14, a tacky resin bindingthe two together. By depositing a suitable conductor on the surface ofthe notches 16 and 22, wires may be placed in these notches to connectthe tape capacitor thus formed into an electric circuit. Wheredesirable, other squares of the tape of FIG. 6 may be stacked on thefirst square of tape to increase the capacity of the capacitor. Theassembled tape capacitor is next cured under heat, the usual curingprocess taking place at about 400 F. A wide degree of latitude intemperature and time is possible, however, depending upon the dielectricmaterial and the resin binder. This curing produces a permanent bond ofthe temporary bond formed by the tacky resin employed as a binder indielectric 26. At any time prior to the curing process the assembledcapacitors may be subjected to ordinary handling to continue themanufacturing process or to package and store for later curing.

It will be readily understood that the size of the capacitor may bevaried by varying the area, the amount of titanate in dielectric 26, andby varying the thickness of the dielectric layer.

In FIG. 8 there is shown a piece oftape made of two layers of the tape24 of FIG. 5, separated by a layer dielectric material 26. The tape ofH6. 8 may be folded or accordion pleated resulting in a self-supportingcapacitor as is illustrated in FIG. 10. Similarly, if it be desired aself-supporting capacitor may be formed by coiling or folding a piece oftape over itself by utilizing appropriate insulating material 34. 'Sucha piece of tape is shown in FIG. 9 and when folded as in FIG. 11 the twostrips of tape 24, 24 are prevented from contacting each other byinsulating layer 34. Leaders 30 and 32 provide connections to each ofthe plates of the folded self-supporting unit. Although this is notnecessary such a condenser may be mounted on awafer in which caseleaders 30 and 32 would be connected to appropriate silvered notches.

As in the construction previously discussed the tape illustrated in.FIG. 8 may be subjected to ordinary handling and may be stored for lateruse. After having been folded .oraccordion-pleated as in FIG. 10 Orafter having added insulation layer 34 to form the tape shown in FIG. 9and then folded .as in FIG. 11 the self-supporting capacitor producedthereby must still. undergo the final curing process to produce apermanent bond.

Obviously many modifications and variations of the present invention.are possible in the light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

What is claimed is:

l. The method of making a capacitor comprising placing a conductivepattern on a non-conductive carrier, impregnating a porous tape withconductive material in a binder component and solvent, coating one sideof the resulting conductive tape with a dielectric material in a binder,placing said prepared tape on said pattern with the dielectric materialadjacent said pattern said binder being in its uncured state, applying.pressure to urge said tape against said pattern excluding all entrappedair and curing the assembled structure under heat whereby saidconductive tape, dielectric coating, conductive pattern andnon-conductive carrier become permanently bonded into a composite unit.

2. The method described in claim 1 in which the pattern is deposited onthe carrier by screening.

3. The method described in claim 1 in which the porous tape isimpregnated by spraying.

4. The method described in claim 1 in which the dielectric coating isapplied by spraying.

5. The method of making a capacitor comprising forming a carrier ofnon-conductive material, placing a conductive pattern on said carrier,impregnating a porous tape with conductive material in a bindercomponent and solvent, coating one side of the resulting conductive tapewith a dielectric material in a binder, placing said prepared tape onsaid pattern with the dielectric mate- ;rial adjacent said pattern saidbinder being in its uncured state, applying pressure to urge said tapeagainst said pattern excluding all entrapped air and curing theassembled structure under heat whereby said conductive tape, dielectriccoating, conductive pattern and nonconductive carrier become permanentlybonded into a composite unit.

6. The method of making a capacitor comprising forming a carrier ofnon-conductive material, depositing a conductive pattern on saidcarrier, firing said carrier and pattern at an elevated temperature topermanently metalize said pattern and to permanently bond said patternto said carrier, impregnating a porous tape with conductive material ina binder component and solvent, coating one side of the resultingconductive tape with a dielectric material in a binder, placing saidprepared tape on said pattern with the dielectric material adjacent saidpattern said binder being in its uncured state, applying pressure tourge said tape against said pattern excluding all entrapped air andcuring the assembled structure under heat whereby said conductive tape,dielectric coating, conductive pattern and non-conductive carrier becomepermanently bonded into a composite unit.

7. The method of making a capacitor comprising forming a carrier ofnon-conductive material, depositing a conductive pattern on saidcarrier, firing said carrier and pattern at anelevated temperature topermanently metalize said pattern and to permanently bond said patternto said carrier, impregntaing a porous tape withconductive material in aresin binder component and solvent, coating one side of the resultingconductive tape with a dielectric material in a resin binder, cutting aportion fromsaid tape, placing said portion on said patternwith-the.dielectricmaterial adjacent said pattern said resin binderbeing in its uncured state, applying pressure to urge said portionagainst said pattern excluding allentrapped air and curing the assembledstructure under heat whereby said portion of conductive tape, dielectriccoating,.conductive pattern and non-conductive carrier becomepermanently bonded into a composite unit.

8. The method of makinga capacitor comprising impregnating a porous tapewith conductive material in a binder component and solvent, coatingoneside of a first length of the resulting conductive tape with adielectric material in a binder, placing one side of a second length ofsaid conductive tape against said dielectric coating on said firstlength said binder being in its uncured state, applying pressure urgingsaid first and second lengths of tape toward one another excluding allentrapped air, applying an insulating layer to one side of the combinedlengths of tape, folding a portion of the resulting combination oflayers over itself at least one time, curingythe folded combination oflayers under heat whereby said lengths of conductive tape and saidcoating of dielectric disposed therebetween become permanently bonded.

9. The method of making a capacitor comprisingimpregnating a porous tapewith conductive material in a binder component and solvent, coating oneside of a first length of the resulting conductive tape with adielectric material in a binder, placing one side of a secondlength ofsaid conductive tape against said dielectric coating on said firstlength said binder being in its uncured state,

applying pressure urging said first and secondlengths of tape toward oneanother excluding all entrapped air, applying an insulating layer to oneside of the combined lengths of tape, coiling the resulting combinationof layers, curing the coiled combination of layers under heat wherebysaid lengths of conductive tape and said coating of dielectric disposedtherebetween become permanently bonded.

10. The method of making a capacitor comprising impregnating a poroustape with conductive material in a binder component and solvent, coatingone side of a first length of the resulting conductive tape with adielectric material in a binder, placing one side of a second length ofsaid conductive tape against said dielectric coating on said firstlength said binder being in its uncured state, applying pressure urgingsaid first and second lengths of tape toward one another excluding allentrapped air, accordion-pleating the resulting combination of layers,curing the pleated combination of layers under heat whereby said lengthof conductive tape and said coating of dielectric disposed. therebetweenbecome permanently bonded.

11. The method of making a capacitor comprising impregnating a poroustape with conductive material in a binder component and solvent, coatingone side of the resulting conductive tape with a dielectric material ina binder, placing two lengths of said coated tape together with saidcoated sides adjacent one another said binder being in its uncuredstate, applying pressure urging said lengths of tape toward one anotherexcluding all entrapped air, applying an insulating layer to one side ofthe combined lengths of tape, folding a portion of the resultingcombination of layers over itself at least one time, curing the foldedcombination of layers under heat whereby said lengths of conductive tapeand said coating of dielectric disposed therebetween become permanentlybonded.

12. The method of making a capacitor comprising irnpregnating a poroustape with conductive material in a binder component and solvent, coatingone side of the resulting conductive tape with a dielectric material ina binder, placing two lengths of said coated tape together with saidcoated sides adjacent one another said binder being in its uncuredstate, applying pressure urging said lengths of tape toward one anotherexcluding all entrapped air, coiling the resulting combination oflayers, curing the coiled combination of layers under heat whereby said20 lengths of conductive tape and said coating of dielectric disposedtherebetween become permanently bonded.

13. The method of making a capacitor comprising impregnating a poroustape with conductive material in a binder component and solvent, coatingone side of the resulting conductive tape with a dielectric material ina binder, placing two lengths of said coated tape together with saidcoated sides adjacent one another said binder being in its uncuredstate, applying pressure urging said lengths of tape toward one anotherexcluding all entrapped air, accordion-pleating the resultingcombination of layers, curing the pleated combination of layers underheat whereby said lengths of conductive tape and said coating ofdielectric disposed therebetween become permanently bonded.

References Cited in the file of this patent UNITED STATES PATENTS1,702,993 Brown Feb. 19, 1929 FOREIGN PATENTS 691,240 Great Britain May6, 1953 718,811 Great Britain Nov. 24, 1954

11. THE METHOD OF MAKING A CAPACITOR COMPRISING IMPREGNATING A POROUSTAPE WITH CONDUCTIVE MATERIAL IN A BINDER COMPONENT AND SOLVENT, COATINGONE SIDE OF THE RESULTING CONDUCTIVE TAPE WITH A DIELECTRIC MATERIAL INA BINDER, PLACING TWO LENGTHS OF SAID COATED TOGETHER